Researchers develop a method for controlling oxygen vacancies in oxides to enhance resistive switching behavior

Oxygen vacancies in oxides are often used in memory devices, yet controlling their mechanism proves to be challenging. Now, Korean researchers have come up with a novel method to control the distribution of the oxygen vacancies using electrostatic potential constraints, thereby enhancing the reliability of device performance. This breakthrough potentially paves the way for next-generation memory devices, multi-bit memristors, analog switches, and neuromorphic computing hardware.

Researchers have shown that managing oxygen vacancies in transition metal oxide structures allows for consistent resistive switching in memory devices.

Oxygen vacancies, which are common functional point defects in various oxides, play a crucial role in memory device technology. This includes "resistive switching devices," which control electrical resistance through the distribution of oxygen vacancies. Given the potential of resistive switching devices for next-generation semiconductor technology, it is crucial to understand the mechanism underlying resistive switching for future advancements of this technology. However, applying this technology is fraught with challenges, particularly in managing the conductance of oxide crystals, resulting in unpredictable and uneven switching behavior.

To address these challenges, a team of researchers from Ajou University, Gachon University, and Sejong University has developed a new method for controlling oxygen vacancies in LaAlO₃/SrTiO₃ (LAO/STO) structures to achieve uniform and consistent resistive switching. Their findings were published in Small on 7 May 2023. 

Associate Professor Hyungwoo Lee from Ajou University, who led the study, says, “While most studies concentrate on the ‘conducting filament’ mechanism, which relies on a small number of point defects at the filament's edge to influence the overall resistance, switching reliability, and speed, our approach takes a distinct path. Instead of relying on the randomly determined geometry of the conducting filament, we have developed a method that focuses on controlling the density of uniformly distributed point defects across the oxide film.”

The team achieved this by imposing electrostatic potential constraints in the LAO/STO structures, ensuring uniform defect distribution and density. This innovative approach reduced the randomness in the movement of the defects and thus provided a solution for reliable performance. Furthermore, evidence of the control of oxygen vacancies was obtained through spectral analysis and Monte–Carlo simulation modeling.

While further research is needed for practically applying this approach, the current study demonstrates effective control of oxygen vacancy distribution. By storing information based on defect concentration (similar to biological ionic channels), the switching characteristics of oxide materials can be enhanced. 

Consequently, this breakthrough paves the way for next-generation memory devices, multi-bit memristors, and analog switching devices, with potential applications in neuromorphic computing hardware as well. “In this regard, our study has opened the door to a future where electronic device technologies based on functional point defects could become a reality,” concludes Dr. Lee.

Reference

*Corresponding author’s email: hyungwoo@ajou.ac.kr 

About Ajou University

Founded in 1973, Ajou University has quickly grown to become one of the top universities in the Republic of Korea. With over 15,000 students and 50 research centers in diverse fields, Ajou University partakes in the largest national research and graduate education project funded by the Korean Ministry of Education. In line with its recently reformed vision, Ajou University’s goal is to change society by connecting minds and carrying out high-impact research to improve the welfare of people in and outside Korea. 

Website: https://www.ajou.ac.kr/en/index.do 

About Associate Professor Hyungwoo Lee 

Hyungwoo Lee is an Associate Professor at Ajou University, specializing in Physics. His group focuses on designing oxide heterostructures to explore emergent physics. Among his research interests are the 2D electron gas (2DEG) at oxide heterointerfaces, ferroelectric polarizations, exotic magnetisms, superconductivity, and quantum transport properties. Additionally, Dr. Lee's team develops resistive switching devices, ferroelectric tunnel junctions, and quantum devices using atomically-designed oxide heterostructures. Prior to his role at Ajou University, he completed postdoctoral training at Chang-Beom Eom's lab at the University of Wisconsin-Madison and earned a Ph.D. in Physics from Seoul National University in 2013.